In a medium saucepan, whisk together sugar, lemon zest, lemon juice, limoncello, eggs, and egg yolk. Cook over medium heat, whisking constantly, until mixture is thickened and bubbly, 6 to 8 minutes. Remove from heat, and whisk in butter until melted.
Pour mixture into a heatproof bowl; cover with plastic wrap, pressing wrap over surface of curd to prevent a skin from forming. Refrigerate for at least 8 hours.
In a large bowl, beat cream with a mixer at medium-high speed until stiff peaks form. Add lemon curd and crumbled cookies, swirling mixture with a knife.
Spoon mixture into individual serving dishes; garnish with crumbled cookies, if desired.
Recipe by Victoria at https://victoriamag.com/lemon-shortbread-fool-recipe/